Devices for reducing electromagnetic interference

Abstract

The electromagnetic interference mitigation device includes a power supply, a power cord, a power supply housing that encloses at least the power supply and is physically isolated from the power cord, a low-value resistor that is in electrical communication with at least the power cord and the power supply, and a capacitor disposed between the power supply housing and a device housing, wherein the device housing encloses the power supply housing and is disposed at a distance from the power supply housing, and the capacitor is formed by the device housing and the power supply housing.

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE This disclosure relates to medical equipment and, more particularly, to systems, devices and methods for mitigating electromagnetic interference associated with medical and laboratory equipment. [Background technology]

[0002] According to leading technology analysts, technology is advancing at an exponential rate. Many industries that once utilized manual tools and primitive processes are being revolutionized by the introduction of microcomputers, sensors, and other modern components. As a result, individuals' homes and businesses now contain an unprecedented amount of computer hardware and circuitry. This proliferation of electronic devices creates two problems related to electromagnetic interference (EMI). First, there are a large number of devices that are prone to EMI-induced errors. Second, there are an even greater number of devices that contribute to EMI.

[0003] EMI can have a devastating effect on the performance of electronic devices, causing operational errors and potentially rendering them inoperable. This problem is exacerbated by the increasing prevalence of EMI-causing devices. Wireless technologies such as mobile phones, portable computers, Bluetooth, GPS, and Wi-Fi are particularly contributing to the EMI problem.

[0004] EMI can be categorized into two types: conducted EMI and radiated EMI. Conducted EMI occurs due to physical contact between conductors, while radiated EMI occurs through induction and is therefore non-contact. Generally, conducted EMI occurs at low frequencies, while radiated EMI occurs at high frequencies. EMI is typically generated by low-performance components such as generators and motors. Many of these components have switch-mode power supplies, which generate both conducted and radiated EMI due to their fast switching speeds.

[0005] EMI can be particularly detrimental to equipment used in hospitals. Devices such as life support systems, vital sign monitors, and ventilators are susceptible to EMI and must be protected from it. In hospitals, the problem is particularly complex because the source of EMI is often other critical medical equipment. Summary of the Invention [Problem to be solved by the invention]

[0006] To mitigate EMI problems, an "x capacitor" can be placed at the power cord input to direct current from the enclosure and wiring back to the power source, preventing it from being conducted along the power cord. While such "x capacitors" often work well, they can increase the ground current that flows to earth. However, unlike other equipment, medical devices require earth-ground currents to be minimized to prevent malfunctions in the patient's electrical equipment. Conversely, a smaller "x capacitor" can reduce ground currents but provide insufficient EMI mitigation.

[0007] It would therefore be desirable to provide a system and method that solves the problem of reducing EMI in environments where grounding is undesirable. Devices often do not meet safety guidelines for EMI in the low frequency range. To reduce low frequency emissions without affecting high frequency emissions, it is desirable for the power supply enclosure to be electrically isolated from ground.

[0008] Additionally, to remedy the shortcomings of current EMI mitigation techniques, it would be desirable to form a capacitor in which the walls of the power supply enclosure and the device enclosure form the plates of the capacitor. [Means for solving the problem]

[0009] In one embodiment, the disclosed invention is an electromagnetic interference mitigation device comprising a power supply, a power cord, a power supply housing enclosing at least the power supply and physically isolated from the power cord, a low-value resistor in electrical communication with at least the power cord and the power supply, and a capacitor disposed between the power supply housing and a device housing, wherein the device housing encloses the power supply housing and is spaced apart from the power supply housing, and the capacitor is formed by the device housing and the power supply housing.

[0010] Additionally, a low-value resistor may be placed in series with the power supply and the power cord. The device may further include a first x capacitor and a second x capacitor, which may be located within the power supply housing. In one embodiment, the capacitors may function as a high-pass filter configured to reduce low frequencies emitted from the power supply.

[0011] In one embodiment, the power supply housing forms a first plate of a capacitor, and the device housing forms a second plate of the capacitor. Additionally, a dielectric material may be disposed between the first and second plates. In one embodiment, the distance between the plates is between 1.397 and 1.778 mm (0.055 and 0.070 inches). The low-value resistor may have a resistance value less than 100 ohms. In one embodiment, a power cord inputs 90 to 264 VAC to the power supply, and the power supply outputs 48 VDC at a maximum of 15.6 amps.

[0012] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate aspects of the present disclosure and, together with the written description, explain the principles of the disclosure. [Brief explanation of the drawings]

[0013] [Figure 1A] FIG. 1 illustrates one embodiment of a preferred electromagnetic interference mitigation. [Figure 1B] FIG. 1 illustrates one embodiment of undesired electromagnetic interference. [Figure 1C]1 illustrates an embodiment of an apparatus configured to mitigate electromagnetic interference. [Figure 2] Graph showing frequency response. [Figure 3] FIG. 1 illustrates an embodiment of a conducted electromagnetic compatibility test apparatus. DETAILED DESCRIPTION OF THE INVENTION

[0014] SUMMARY OF THE INVENTION Apparatuses, systems and methods for mitigating electromagnetic interference in electronic equipment are described below. In this disclosure, singular words are to be construed as including their plural meanings unless otherwise specified. Furthermore, the term "comprises" is not limiting. "Or" is equivalent to "and / or" unless otherwise specified. Even where preferred ranges are described, there may be embodiments that operate outside the preferred ranges unless expressly stated otherwise.

[0015] An example of ideal electromagnetic interference mitigation is shown in Figure 1A. For example, the device shown in Figure 1 is a functioning hospital device, but does not generate EMI. For purposes of disclosure, Figure 1A illustrates the desired result of the EMI mitigation method.

[0016] Figure 1B shows an example of a device where low frequency emissions can travel through the device's ground. For purposes of disclosure, Figure 1B shows a system that is generating an undesirable amount of EMI.

[0017] As shown in FIG. 1C, the device 100 includes a device housing 102, a power supply housing 104, a power supply 106, a power cord 108, a first x capacitor 110, a second x capacitor 112, a low-value series resistor 116, and a capacitor / high-pass filter 114.

[0018] The capacitor 114 is formed when the distance between the device housing 102 and the power supply housing 104 is, for example, 0.055 to 0.070 inches (1.397 to 1.778 mm) or any other suitable distance. In one embodiment, the capacitor distance is measured between the walls of the device housing 102 and the power supply housing 104 at the point where the two housings 102 / 104 are physically closest to one another. However, in other embodiments, the capacitor distance may be measured in other ways, for example, at the location where one of the housings holds the most charge. In one embodiment, each housing 102 / 104 has four perimeter walls, a top wall, and a bottom wall. In such an embodiment, the capacitor 114 is formed along two corresponding walls of the housings 102 / 104. Furthermore, in such an embodiment, the distance between two corresponding walls (the walls that form the capacitor 114) may be shorter than the distance between other corresponding walls (e.g., the distance between the left wall of the device housing 102 and the left wall of the power supply housing 104). Thus, the walls of the housing 102 / 104 that form the capacitor 114 may be the corresponding walls that are closest to each other, however, in other embodiments, the capacitor 114 may be formed by any number or combination of walls that are any distance apart.

[0019] In one embodiment, the capacitor distance is user adjustable, and can be adjusted manually, automatically, or by an attached computer. In one embodiment, a servo motor or other similar component is placed between the housings 102 / 104 to allow the capacitor distance to be changed. In one embodiment, the variable distance is fixed and not adjustable. In one embodiment, a winch, wedge, or screw is placed between the power supply housing 104 and the device housing 102 to allow fine adjustment of the capacitor distance. Such an embodiment, and similar alternative embodiments, are shown in FIG. 1C.

[0020] The device 100 includes a device housing 102 and a power supply housing 104. In many embodiments, the power supply housing 104 encloses a power supply 106. In one example, the power supply 106 has an electrical input / output, such as an input of 90-264 volts AC and / or an output of 48 volts DC at up to 15.6 amps. However, the power supply 106 may have any suitable electrical input or output. The power supply 106 may be, for example, an AC power source, a DC power source, or another common type of power source. In an alternative embodiment, the power supply housing 104 encloses multiple power supplies 106. In yet another embodiment, the device housing 102 encloses multiple power supply housings 104.

[0021] In one embodiment, both the device housing 102 and the power supply housing 104 are constructed of metal and function as electrical conductors. However, in other embodiments, the device housing 102 and the power supply housing 104 are formed from a variety of suitable materials. For example, in another embodiment, the device housing 102 and / or the power supply housing 104 are constructed of or include a thin film, foil, or electrolyte. In an alternative embodiment, one of the two housings is constructed from a material designed to be less conductive than the other. In such an alternative embodiment, the less conductive housing may reduce the overall effectiveness of the capacitor formed by the two housings. This alternative embodiment may reduce the effectiveness of the high-pass filter 114, which may be beneficial for users who want to reduce the proportion of high frequencies passing through the capacitor 114.

[0022] In one embodiment, a dielectric material is disposed between the device housing 102 and the power supply housing 104. For example, in some embodiments, glass, Teflon, polystyrene, titanium dioxide, barium titanate, or other dielectric material is disposed between the two housings 102 / 104. In one embodiment, the power supply housing 104, the device housing 102, and any other housings or components are insulated. In one embodiment, the power supply housing 104, the device housing 102, and any other housings or components are insulated from electricity, heat, vibration, or sound.

[0023] In yet another embodiment, the device housing 102 and the power supply housing 104 do not form the capacitor 114. In such an alternative embodiment, a separate capacitor is disposed between the two housings 102 / 104. Also, the power supply housing 104 may not enclose the power supply 106. In such an embodiment, another component, such as a metal plate, may be in electrical communication with the power supply 106, with this other component forming one half of the capacitor 114 and the device housing 102 forming the other half. In one embodiment, the power supply 106 is connected to a separate ground or other cable configured to transmit low frequencies.

[0024] While in some embodiments, capacitor 114 functions as a high-pass filter, capacitor 114 may also be configured as a low-pass filter. Referring to FIG. 2, an embodiment of electromagnetic interference mitigation device 100 reduces low-frequency emissions. FIG. 2 illustrates how an embodiment of the presently disclosed invention reduces the amplitude of emissions in the low-frequency range. Referring to FIG. 2, an embodiment of electromagnetic interference mitigation device 100 is configured to reduce low-frequency emissions, although the invention is not limited to the slope and characteristics illustrated in FIG. 2. In other embodiments, a user of device 100 can adjust the degree of effectiveness of device 100 depending on the particular application. In such embodiments, the presently disclosed invention may have a greater or lesser impact on emissions than the example illustrated in FIG. 2.

[0025] In some embodiments, the power supply housing 104 and / or the device housing 102 are constructed from a single continuous sheet. For example, in such continuous-sheet embodiments, the entire housing 102 / 104 can be rolled, 3D printed, molded, or otherwise manufactured so that the housing 102 / 104 is one piece. Alternatively, in other embodiments, one or both of the power supply housing 104 and the device housing 102 are constructed from multiple sections. For example, in such alternative embodiments, both housings 102 / 104 have a top, bottom, left side, right side, front side, and back side. Furthermore, the top, bottom, left side, right side, front side, and back side may be separate components that are fastened together to form the device housing 102 or the power supply housing 104.

[0026] In another embodiment, neither of the housings 102 / 104 is made entirely of the same material. For example, 90% of the housing is made of a metal known in the art to function well as a conductor, and 10% of the housing is made of a material known as a poor conductor or insulator. Such an embodiment is useful in applications where there are sensitive components that must be placed within the housing but must not be placed within a certain proximity to the conductive material.

[0027] Also, in one embodiment, the device housing 102 and / or the power supply housing 104 may be mesh, chain link, foil, or other malleable material disposed around the components disposed therein. For example, in applications where the use of a traditional rigid housing that is geometrically or physically impermeable is not feasible, the malleable material may "wrap" the components that would normally reside within the housing. In this alternative embodiment, the malleable material comprising the housing may have many of the same properties (e.g., conductivity, material, dielectric properties, etc.) as traditional housings.

[0028] In one embodiment of the electromagnetic interference mitigation device, the device further includes a low-value resistor 116. The low-value resistor 116 is, for example, less than 100 ohms. In certain embodiments, a lower resistance value results in a higher amplitude of low frequency conduction and / or a higher resistance value results in an increased amount of radiated emissions. In one embodiment, the resistance value is, for example, approximately 56 ohms. In another embodiment, the low-value resistor 116 is greater than 100 ohms. In one embodiment, the low-value resistor 116 is connected in series with at least the power source 106 and ground and / or power cord 108. In another embodiment, the low-value resistor 116 is connected in parallel with at least the power source 106 and ground and / or power cord 108.

[0029] In yet another embodiment, the electromagnetic interference mitigation device 100 includes a plurality of low-value resistors 116. In such an alternative embodiment, the plurality of low-value resistors 116 are connected in series or parallel with at least the power source 106 and the ground and / or the power cord 108. In one embodiment, the low-value resistors 116 are variable resistors. In such an embodiment, the low-value resistors 116 are easily adjustable by a user.

[0030] EMI mitigation apparatus 100 may be configured to provide suppression for conducted EMI frequencies between 100 Khz and 30 Mhz along the AC power cord 108 of a device under test. Referring to Figure 3, EMI emissions may be measured by connecting the AC power cord 108 of apparatus 100 to a line impedance stabilization network 304, which is further connected to a spectrum analyzer 302. Line impedance stabilization network 304 is connected to a mains power supply 306. However, in alternative embodiments, other methods and / or components may be used to measure conducted EMI emissions.

[0031] Alternative embodiments of the disclosed invention provide for the suppression of conducted electromagnetic interference outside the 100 Khz to 30 Mhz range. In yet other embodiments, the apparatus 100 suppresses conducted electromagnetic interference emissions traveling along components other than the AC power cord 108. For example, in such embodiments, the electromagnetic interference mitigation apparatus 100 is configured to suppress emissions along, but not limited to, cords attaching peripheral devices to a device under test, a frame or structure supporting the device under test, or other electronic equipment in close proximity to the device under test.

[0032] In one embodiment, the electromagnetic interference mitigation device includes a power source, a power cord, and a power supply enclosure that encloses at least the power source. In such an embodiment, the power source may be physically isolated from the power cord. However, the power source may be in electrical communication with the power cord (e.g., via additional circuitry, wires, etc.). The device may include a low-value resistor and a capacitor. The low-value resistor is in electrical communication with at least the power cord and the power source, and the capacitor is located between the power supply enclosure and the device enclosure. In one embodiment, the device enclosure encloses the power supply enclosure, the device enclosure is located away from the power supply enclosure, and the capacitor is formed by the device enclosure and the power supply enclosure. The low-value resistor is located in series with the power source and the power cord.

[0033] In yet another embodiment, the device includes a first x capacitor and a second x capacitor, the first x capacitor and the second x capacitor being disposed within the power supply housing. The capacitors may be configured as a high-pass filter configured to reduce low frequencies emitted from the power supply. The power supply housing forms a first plate of the capacitor, and the device housing forms a second plate of the capacitor. In yet another embodiment, a dielectric material is disposed between the first plate and the second plate. The two plates are also spaced apart from each other by a distance of 1.397 to 1.778 mm (0.055 to 0.070 inches). However, the distance may be any other suitable value. In one embodiment, the low-value resistor has a resistance of less than 100 ohms. In another embodiment, a power cord inputs 90 to 264 VAC to the power supply, and the power supply outputs 48 VDC at a maximum of 15.6 amps.

[0034] While the present invention has been described in conjunction with the above embodiments, it will be apparent to those skilled in the art from the foregoing description that many alternatives, modifications, and variations are possible. Accordingly, the above-described embodiments of the present invention are intended to be illustrative and not restrictive. Various changes may be made without departing from the spirit and scope of the present invention.

Claims

1. An electromagnetic interference mitigation device, comprising: Power supply and Power cord and a power supply enclosure that encloses at least the power supply and is physically isolated from the power cord; a low-value resistor having a resistance of less than 100 ohms in electrical continuity with at least said power cord and said power source; a capacitor disposed between the power supply housing and the device housing, the device housing surrounds the power supply housing; the device housing is disposed at a distance from the power supply housing, The electromagnetic interference mitigation device, wherein the capacitor is formed by the device housing and the power supply housing.

2. 2. The electromagnetic interference mitigation device of claim 1, wherein said low value resistor is placed in series with said power source and said power cord.

3. 2. The electromagnetic interference mitigation device of claim 1, further comprising a first x capacitor and a second x capacitor, said first x capacitor and said second x capacitor being disposed within said power supply enclosure.

4. 10. The electromagnetic interference mitigation device of claim 1, wherein the capacitor is configured to provide suppression for conducted electromagnetic interference frequencies between 100 Khz and 30 Mhz.

5. 2. The electromagnetic interference mitigation device of claim 1, wherein the power supply housing forms a first plate of the capacitor and the device housing forms a second plate of the capacitor.

6. 6. The electromagnetic interference mitigation device of claim 5, wherein a dielectric material is disposed between the first plate and the second plate.

7. 7. The electromagnetic interference mitigation device of claim 6, wherein said distance is between 0.055 and 0.070 inches.

8. 2. The electromagnetic interference mitigation device of claim 1, wherein said power cord inputs 90-264 VAC to said power source, and said power source outputs 48 VDC at a maximum of 15.6 amps.

Images